Evaluation of Measurement Uncertainties of Bacillus cereus in Infant Formula Milk Powder

Abstract:

[Objective] The study evaluated the measurement uncertainties of Bacillus cereus (B. cereus) in milk powder samples to analyze the factors influencing the measurement of B. cereus. [Method]According to the evaluation procedure in JJF 1059.1—2012, the uncertainties of the plate counting results for B. cereus in infant formula milk powder were evaluated through the following five steps: identifying uncertainty sources, establishing the measurement model, assessing standard uncertainties, calculating the combined standard uncertainties, and determining the expanded uncertainties. Contributions from each uncertainty component were analyzed, and corresponding measures were suggested to enhance the accuracy of the measurement results. [Result]At a confidence level of 95% and with 9 degrees of freedom (ν), the k value was determined to be 2.26, and the expanded uncertainty (U₉₅) was 0.20. The findings indicated that the largest source of uncertainties during the counting process for B. cereus arose from repeated measurements, followed by the uncertainty introduced by growth rate in culture media. [Conclusion]The study lays a foundation for the quality control of B. cereus and provides technical guidance for improving the evaluation of uncertainties in the microbiological field.